His first appearance is referenced by the White Ninja Leader during the mission Revenge of The Ninja in which he tells Crypto that he might know the location of the hidden KGB base in Takoshima, but has been kidnapped and is being held in Castle Kuro.
In the mission Dr. Go!, Crypto must rescue him and bring him to the White Ninja Leader at the entrance of the castle, then he must destroy it.
In the next mission, the player must complete three tasks for Dr. Go! reuniting the fragments of a photo containing the location of the KGB base. Crypto can find them from the Black Ninja Leader, Professor Yuki and Agent Sascha Soysorski.
- Dr. Go! is obviously based in Dr. Julius No, an antagonist of the James Bond series.